Question

1.

a. How do you represent chemical reactions by using chemical equations? Please provide an example.

b. How do you calculate the amount of energy released/absorbed in a chemical reaction by using bond energies? Please provide an example.

c. How do you determine whether a reaction is wxpthermic or endothermic based on the sign from the process above. Please provide an example.

Answer 1

Ans

a) Try writing the compounds mentioned in the chemical reactions in their formula form , and place them in the equation left or right as mentioned.

For example : A reacts with B to form C and D

Equation : A + B = C + D

b) Energy is required to break the bonds and released when the bonds are formed. The net sum of these energies , form the basis of enthalpy of the reaction.

For ex, AB + C = AC + D

Suppose A-B bond energy is 100 KJ/mol

and A-C bond energy is 150 KJ/mol

So enthalpy = 150 - 100 = +50 KJ

c) Always look for the sign of enthalpy to detemine whether the reaction is exothermic or endothermic.

If the sign is positive , the reaction is endothermic , if the sign is negative , the reaction is exothermic.